The invention relates to a shutter controlling aid means for use with a camera which incorporates an electrical shutter and which is adapted to utilize an ordinary (not auto) strobo unit.
A camera incorporating an electrical shutter such as the one of direct photometry type, for example, in which a photometric circuit is also responsive to an illumination from an ordinary strobo unit to operate the shutter circuit, operates to close the shutter in a daytime synchronized photographing operation when the sum of natural light and illumination from the ordinary strobo unit reaches a given level. It is also operative to close the shutter when a given amount of exposure is reached in response to either natural light or illumination from an ordinary strobo unit alone.
Where the exposure provided by natural light is small and it is necessary to use an ordinary strobo unit to take a picture, it is necessary to determine if the exposure provided by the ordinary strobo unit is sufficient for a preselected diaphragm aperture and a given distance to an object being photographed. Where the illumination from the ordinary strobo unit is insufficient, the shutter remains open after the termination of the illumination from the ordinary strobo unit, and the shutter will be closed only when the deficit is compensated for by natural light. If the magnitude of the deficit is very small, the shutter will be closed by a short interval after the termination of the illumination from the strobo unit, presenting no substantial problem. However, when an incorrect selection is made such that the illumination provided by the ordinary strobo unit is only one-half the level required, the remaining half must be supplied by natural light of low brightness, resulting in a prolonged shutter open period. When the camera is held by hand, any movement caused may result in a doubled photographing. Also, the shutter will be maintained in an open condition even if the deficit is small when the contribution of natural light is small for a preselected diaphragm aperture, preventing the camera from being prepared to perform the next photographing operation. When the shutter continues to be open for a period on the order of ten or twenty seconds, there will be a great influence psychologically on the user. In view of these considerations, it will be desirable to detect the illumination from a strobo unit to cause a forced closure of the shutter when taking a flash photograph using an ordinary strobo unit in order to improve the yield of the resulting photographs and to remove the feeling of restlessness even though some photographs may be under-exposed to a degree.